The merging of GPS and the Web
Kurt Cagle
Published: 14 Jul 2003 10:57 BST
A language is born
One means to encode routes has been proposed by Charon, the GPSml markup language, to be submitted as a note to the W3C later this year. In this XML-based system, a GPSml document consists of one or more collections of three principal types: a waypoint, a route (a named collection of waypoints), or a track (which combines locations with a time coordinate). A waypoint consists of a position, an identifier that defines a waypoint relative to the document, and a display attribute that is intended to provide some indicator of how the waypoint should be visually identified.
In some respects, it's the identifier that is most critical for Web deployment. An identifier can be any label, and doesn't have to be unique beyond the scope of the document. However, it can be. One way of understanding the importance of this identifier is to associate it with a Uniform Resource Identifier (URI). With such a URI, you could effectively assign to that location an application that will run when the location is referenced in some manner (you get within five feet of that node, for instance). This application could be a Web service, retrieving contextual information about the location; it could notify the tracking application to recheck the route that you're on to make sure it is still the most efficient one; it could bring up a list of sales in all of the adjacent stores. It could even retrieve a message that's read out loud by a vox program: "Go up the escalator past the Radio Shack store, until you come to the fountain, then turn right."
Technological consequences
One of the more interesting, and potentially troubling, aspects of a GPS device is that it has a unique identifier, which can be associated with its owner. This identifier can be used as part of a person's XML profile. Marketers live for this kind of information; even without knowing anything about you, a marketer could read the identifier being transmitted to Web services giving GPS information for the device and develop a profile showing that the last three times you came to this shopping centre, you bought clothes from Next and a network card from Dixons. This kind of demographic information could be used both in general a manner, to see which stores need to be better promoted, and in an individual manner, to offer a discount on network cables for that card you bought last time.
A given point in space may have different meanings to different people, of course. Typically, any application that uses GPS positioning would define its own GPSml document that would be provided as part of a Web service, creating the relevant context. That's why a GPS location by itself is insufficient to be used as a URL--there may be many contexts associated with the location, and it is only by accessing the appropriate service that a given context can be applied.
Geeplogs are next
The Really Simple Schema (RSS) specification is currently gaining ascendancy in the world of blogs and news feeds, but in the future it, or something very much like it, will emerge as a way to publish public GPS contexts that can be queried about a given area. Of course, the least interesting will be the ones published by the owners or promoters of the site. More likely (and lively) will be the GPS equivalents to blogs, in which a person could narrate a specific tour with his or her relevant commentary, possibly with photographs, video feeds, and links to subjects that may or may not be approved by management. There could be several such geeplogs (GP logs) in any given space, providing a virtual metaphorical context to the area -- digital graffiti.
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